EVIDENCE FOR THE PRESENCE OF MALTASE AND α‐GLUCOSIDASE ISOENZYMES IN BARLEY

Abstract

An examination of the development of α‐glucosidase and maltase activities (as measured by the hydrolysis of p‐nitrophenyl α‐D‐glucoside and maltose respectively) indicated that two genotypes of Glacier barley had the same general pattern of enzyme development. However, the development of α‐glucosidase activity followed a different course from that of maltase activity suggesting that separate enzyme proteins are involved in hydrolysing these substrates. Further evidence that separate enzyme proteins were responsible for hydrolysis of maltose and p‐nitrophenyl α‐glucoside was obtained by column chromatography of extracts of germinated barley which indicated the presence of two maltases and two α‐glucosidases. The maltases and the α‐glucosidases differed in molecular weight, pH of optimum activity and in thermostability. When isomaltose was used as a substrate the optimum pH and behaviour on gel chromatography were coincident with that of maltase activity but different from the α‐glucosidases. 1987 The Institute of Brewing & Distilling